Protein markers associated bone marrow stem cell differentiation into early progentior cells

ABSTRACT

A novel cytosolic 58 kd phosphoprotein induced during bone marrow stem cell (BM) differentiation into dendritic cells (DC) during in vitro cultivation with the cytokine GM-CSF by addition of antisera to an 82 kd BM cell surface protein generating cultivatable dendritic progenitor cells (DP). Genes, methods for preparing them as well as early DP have been provided. Potential uses/advantages lie in the study of BM differentiation and innate immunity due to stimulatory/inhibitory DC, contribution of BM and DP to inflammation during infection and carcinogenesis, tumor promotion/regression, identification of BM-derived blood cells, T-cell activation/regulation/tolerance and inflammation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 12/590,989, filed Nov. 18, 2009, which is a divisional of U.S.patent application Ser. No. 11/283,005, filed Nov. 18, 2005, now U.S.Pat. No. 7,642,045, which claims the benefit of U.S. ProvisionalApplication No. 60/629,110, filed Nov. 18, 2004, all of which are herebyincorporated herein by reference.

SEQUENCE LISTING

The file titled “ISU-0001 sequence listings copy.txt”, created Jun. 19,2012 and comprising 10 kilobytes, which is recorded on the accompanyingcompact disc titled “Sequence ID Nos. 1-6 (Amended),” is herebyincorporated herein by reference.

DESCRIPTION

This invention resides in the discovery of a novel marker duringdifferentiation of bone marrow stem (BM) cells into progenitors, theearly stage of dendritic cells (DCs). Such protein is prepared byincubating BM cells with anti-DC antibodies, e.g., antisera, and then byisolating the protein, i.e., by separating it from the majority ofcomponents of a BM cell lysate following incubation with the anti-DCantibodies. The latter contains antibody to a BM cell surface 82 kdprotein (CSP82). Specific antisera to CSP82 kd can also induce the novelmarker.

The specific marker discovered by the inventors in mouse BM cell lysatesis DP58. DP58 is a cytosolic phosphoprotein having a molecular weight ofapproximately 58 KD (SDS-PAGE), that is induced by incubation of BMcells with anti-DC or anti-CSP82 antibodies. The primary proteinsequence of DP58, as determined by peptide mass fingerprinting, isprovided in SEQ ID NO: 3. Computationally predicted cDNA sequence ofDP58 is also cited as accession no. NP_(—)780664 (NCBI data base).

Having a marker for activation of BM differentiation is important forseveral reasons including because it allows scientists to determine whatevents trigger differentiation of undifferentiated progenitor DCs. Inthe absence of such marker, it is not practically possible to determinewhen differentiation has begun and therefore it is difficult todetermine what events, e.g., cytokine induction, receptors involved inthe initiation of differentiation, role and fingerprint of infiltratingbone marrow derived dendritic progenitors during infection and/or tumorgrowth/regression.

Thus, in one aspect; this invention comprises an anti-DP58 antibody,which can be used to readily identify when differentiation of BM cellsto DCs has begun. The anti-DP58 antibodies of the invention includepolyclonal as well as monoclonal antibodies, anti-DP peptide antibodies,as well as antibody derivatives, e.g., single chain antibodies andfragments and hybrids of antibodies and single chain antibodies, andother polypeptides that comprise a region that binds to the sameepitopes as one or more polyclonal antibodies in anti-sera.

In a related aspect, this invention comprises a method for generatingundifferentiated progenitor DCs comprising incubating BM cells withanti-DC antibodies or specifically with anti-CSP82 antibodies. Presenceof a growth factor, e.g., GM-CSF, facilitates the development. Suchcells are herein referred to as BM4 cells because they are optimally,but not only, produced by incubation of BM cells with anti-DC antiserafor 4 hours.

The invention further resides in the discovery of a BM cell surfaceprotein, CSP82, an 82 kd glycoprotein which is activated by anti-DC serato induce expression of DP58. This protein can also be isolated, i.e.,removed from BM cells, by techniques known to persons of skill in theart. Antibodies to CSP82 can also induce DP58, and generate BM4progenitor cells from BM stem cells. In immunofluorescent staining,CSP-82 reveals itself as a surface protein and detergent is needed tosolubilize it for biochemical studies. The protein was isolated bySDS-PAGE from immunoprecipitate prepared from lysates by using anti-DCantibody and confirmed by western blot. The SDS-PAGE-derived proteinband of 82 kd was sequenced by HPLC-mass spectrometry as for DP58. Theprimary sequence of CSP-82 is shown below as Sequence ID No. 1:

SEQ ID NO: 1   1 MRLLIPSLIF LEALGLCLAK ATTVRWCAVS NSEEEKCLRW     QNEMRKVGGP  51 PLSCVKKSST RQCIQAIVTN RADAMTLDGG TMFDAGKPPY     KLRPVAAEVY 101 GTKEQPRTHY YAVAVVKNSS NFHLNQLQGL RSCHTGIGRS     AGWKIPIGTL 151 RPYLNWNGPP ASLEEAVSKF FSKSCVPGAQ KDRFPNLCSS     CAGTGANKCA 201 SSPEEPYSGY AGALRCLRDN AGDVAFTRGS TVFEELPNKA     ERDQYKLLCP 251 DNTWKPVTEY KECHLAQVPS HAVVSRSTND KEEAIWELLR     QSQEKFGKKQ 301 ASGFQLFASP SGQKDLLFKE SAIGFVRVPQ KVDVGLYLTF     SYTTSIQNLN 351 KKQQDVIASK ARVTWCAVGS EEKRKCDQWN RDSRGRVTCI     SFPTTEDCIV 401 AIMKGDADAM SLDGGYIYTA GKCGLVPVLA ENQKSSKSNG     LDCVNRPVEG 451 YLAVAAVRRE DAGFTWSSLR GKKSCHTAVD RTAGWNIPMG     LLANQTRSCK 501 FNEFFSQSCA PGADPKSNLC ALCIGDEKGE NKCAPNSKER     YQGYTGALRC 551 LAEKAGNVAF LKDSTVLQNT DGKNTEEWAR NLKLKDFELL     CLDDTRKPVT 601 EAKNCHLAIA PNHAVVSRTD KVEVLQQVVL DQQVQFGRNG     QRCPGEFCLF 651 QSKTKNLLFN DNTECLAKIP GKTTSEKYLG KEYVIATERL     KQCSSSPLLE 701 ACAFLTQ

Another aspect of the invention is antibodies directed to CSP82 (orunique peptides corresponding to specific regions of CSP 82 sequence)including, as discussed above, derivatives of such antibodies thatretain binding specificity for the CSP82 epitopes.

One aspect of the invention includes a peptide having the sequence shownbelow as Sequence ID No. 2:

SEQ ID NO: 2 IPIGTLRPYLNWNGPPASLE

Another aspect of this invention is the full length DP58 protein havingthe sequence shown below as SEQ ID NO: 3 (and isoforms thereof):

  1 MDEGSEVSTDGNSLIKAVHQSRLRLTRLLLEGGAYINESND     RGETPLMIAC 51 KTKHVDQQSVGRAKMVKYLLENSADPNIQDKSGKSALMHAC     LERAGPEVVS101 LLLKSGADLSLQDHSGYSALVYAINAEDRDTLKVLLSACQA     KGKEVIIITT151 AKSPSGRHTTQHHLNMPPADMDGSHPPATPSEIDIKTASLPL     SYSSETDLT201 LFGFKDKELCGGSDNTWDPDSPPRKPVIATNGPKLSQAPAWI     KSTPSLKHQ251 ARVASLQEELQDITPEEEIAYKTNALALSKRFITRHQSIDVK     DTAHLLRAF301 DQVNSRKMSYDEINYHSLFPEGSQTSVEIPTDRDPDSNQIF     ASTLKSIVQK351 RNSGANHYSSDSQLAEGVTPPTVEDGKAAKKKIFAPSPSLLS     GSKELVEPA401 PPGPLSRRNHAVLERRGSGAFPLDHSLAQSRPGFLPPLNVNP     HPPITDIGV451 NNKICGLLSCGQKALMPTAPIFPKEFKTKKMLLRRQSLQTEQ     IKQLVNF

The other aspect of the invention includes a peptide having the sequenceshown below as SEQ ID NO: 4:

KMVKYLLENS ADPNIQDKSG

Another related invention is induction of DP58 from human cord bloodstem cells by similar use of anti-DC antibodies as described earlier.

It will also be apparent to the person of ordinary skill in the art toprepare nucleotide sequences that encode DP58 or CSP82. Such sequencescan be derived from mRNA to prepare cDNA or directly from genomic DNA,by genetic engineering techniques, e.g., PCR, cloning, or by synthetictechniques, e.g., direct synthesis of computationally determinedsequences. Antisense DNA or RNA can also be prepared to suppressexpression of DP58.

U.S. Pat. No. 6,479,286 discloses that IL-3 cultured expandedpopulations of monocytes are suitable for in vitro differentiation intoDCs and describes various applications of said discovery. U.S. patentapplications 2003/0104569 and 2003/0194803 are also of interest. Thesethree references are incorporated herein by reference as though fullyset forth.

This invention is more fully illustrated in the Examples that follow.This description is intended to be illustrative and not limiting. Whilethis invention is described with respect to murine-derived DP58, it willbe appreciated that analogous proteins exist in other species and can beisolated and utilized in accordance with this invention. Additionally,while this disclosure describes certain illustrative embodiments of theinvention, including the preferred embodiments thereof, and usesthereof, other embodiments and uses will be apparent to persons ofordinary skill in the art.

EXAMPLES Example 1 DP58

This existence of a common multipotent progenitor DC (pDC) implies thatthe commitment to DC occurs early in response to a specific cytokinemicroenvironment. Cytokines, GM-CSF in particular, function as theprimary growth factor promoting mouse BM differentiation into DC,whereas GM-CSF and IL4 are both required for human hematopoietic stemcell (HSC) [1]. This ability of GM-CSF to induce mouse BMdifferentiation in vitro led us to develop specific antibody reagentsfor identifying molecular markers associated with the early events in DCdevelopment. We describe a novel cytosolic 58 KD Phosphoproteinassociated with early DC progenitors when there is no clear-cut evidenceof any specific DC subtype. Since this protein is induced during BMdifferentiation into common uncommitted early pDC [2,3], we designatedit as DP58 after DC progenitors. The sequence of DP58 matches with noknown protein sequences in the NCBI database, but it has been positivelyidentified with a RIKEN cDNA in the Gene Bank with a Z score of 2.43using peptide mass fingerprinting. To our knowledge, this is the firstreport implicating a cytosolic Phosphoprotein as one molecular hallmarkof early DC progenitors. Unphosphorylated DP58 isoform has also beenidentified in adult neuronal nuclei using anti-DC and anti-DP58 antibodyreagents, PCR technology, flow cytometry, and by fluorescent, andconfocal microscopy. It is expected that like BCL3, DP58 functions as ananti-apoptotic mechanism in mature neurons. Thus, phosphorylated andunphosphorylated DP58 can be used to monitor differentiation status indeveloping brains as well as in diseased states.

Materials and Methods

Mice. BALB/c mice from Harlan Sprague Dawley (Indianapolis, Ind.) werebred in the animal facility of Indiana State University. The UniversityAnimal and Use Committee (ACUC) approved all animal experiments.

Cells and antibodies. Phenotyping was done using fluorescent monoclonalantibodies to CD11b, CD11c, MHCII, CD117, B220, CD86, and CD80 (all fromeBioscence, USA), DEC-205 (Serotec, UK). Anti-phosphotyrosine (Zymed,USA) was used for biochemical characterization. Other materials includedgoat anti-rabbit-Ig HRP, rabbit anti-mouse-Ig (ICN, USA), and. WesternBlot reagents were purchased from Pierce, USA).

Dendritic cells generation [4]. Bone marrow cells were prepared byflushing off the femurs and tibiae of BALB/c mice. Cells were cultivatedin Iscove's modified Dulbecco's medium (IMDM) supplemented with 10% FBSand 10 ng/ml of recombinant murine Granulocyte macrophage colonystimulating factor (GM-CSF), (eBioscience & Peprotech, USA) for 6 daysat 37° C. degree in 5% CO2. Non-adherent cells were removed on day 2 and4 of culture, and fresh IMDM plus GM-CSF were added. DCs generated werephenotyped by flow cytometry and on a regular basis by fluorescentmicroscopy.

DC6 lysates preparation for antisera development: An emulsion containingequal volume of complete Freund's adjuvant (CFA) and DCs (1-3×10⁷cells/ml) in 0.02% SDS solution in PBS was used to immunize threerabbits intradermally. Every 10 days they were bled and boosted with DClysates emulsified in incomplete Freund's adjuvant (IFA).

Preparation of specific rabbit antibody reagents by repeated adsorption,salt fractionation has also been identified and protein Achromatography. The sera obtained after multiple immunizations wereadsorbed primarily on splenocytes, liver tissues, dendritic cells, andmyeloma X63-Ag8.653 cells. Further adsorption was done, as needed, withfresh or formalin-fixed BM cells. This was followed by 50% saturatedammonium sulfate precipitation, dialysis and protein A chromatography.One specific antibody reagent thus prepared was initially used toidentify novel protein DP58 in dendritic cell progenitors.

Generation of progenitor BM cells. 1×10⁷ BM cells were incubated withadsorbed rabbit antisera for 4 hr on ice to generate BM4 cells, whichwere then treated with 1 ml of a lysis buffer12 containing 0.5% NP40 and0.5% MEGA9 plus 10 μl of protease inhibitor, and left on ice for 30 minbefore analysis by SDS-PAGE.

SDS-PAGE and western blot. Lysates prepared according to Elvin et. al.[5] were subjected to 12.5% SDS-PAGE [6], followed by western blottingon nitrocellulose. Primary antibody was rabbit antisera (adsorbed withBM-fresh) and secondary antibody was commercially available antibodyGoat anti-rabbit-Ig HRP. Super Signal West Pico chemiluminescentsubstrate (Pierce, USA) was used to visualize proteins on films.

Immunoprecipitation. This was done as described [6,7] using protein A toisolate specific immune complex formed by mixing cell lysates with theadsorbed rabbit antibody reagent. The specific protein band obtained bySDS-PAGE band was isolated and sequenced by peptide mass fingerprintingat the Proteomics Core Laboratory of Dr. Wang Mu, Indiana UniversitySchool of Medicine.

Rabbit antisera against DP58 peptide: This was done using a conjugate ofkeyhole limpet hemocyanin (KLH) with a peptide, SEQ ID NO: 4(KMVKYLLENSADPNIQDKSG), as the immunogen (100 μg/injection). This wasadministered intradermally as an emulsion of the conjugate initiallywith CFA and later with IFA, and the rabbits, were bled at 10 days'interval. Purification was carried out by salt fraction using 50%saturated ammonium sulfate followed by affinity chromatography onKLH-sepharose column. Unbound fraction was the source of anti-DP58antibody.

Results

Fifty-Eight kiloDalton Protein Identified as DP58

To identify DP58, the freshly harvested BM cells were treated with theadsorbed rabbit anti-DC antisera reagent on ice for 4 hr. This reagentwas protein A-purified after repeated adsorption on BM-derived immatureDCs and mouse myeloma as described in Materials and Methods. BM cellsobtained after 4 hr incubation with the reagent, termed BM4 cells, wereexposed to a lysis buffer, and the lysates were subjected to SDS-PAGE,and western blotting. We used for western blot the same specificantisera reagent but adsorbed additionally on fixed BM cells. Controlswere run using lysates of BM cells that were treated with normal rabbitserum, rabbit anti-IgG or anti-CD11c monoclonal antibodies. The resultsshowed that a 58 Kd protein (DP58) was detectable only in BM4 celllysates using rabbit antisera reagent at 1:200,000 dilution. Incontrast, the lysates of the fixed or fresh BM cells (undifferentiated)exhibited no DP58 protein, even with a higher concentration of theantibody reagent. Since DP58 protein was discerned only in the lysatesof BM4 cells, but not of fresh or fixed BM cells, this suggests thatthis protein was induced as a cytosolic protein.

Next we determined the time course for induction of DP58. The resultsindicated that the induction was detectable in BM cells within 30minutes, although the protein band was most discernible after 4 hr inBM4 cells. Clearly, this adsorbed rabbit anti-DC reagent facilitatesdifferentiation of BM cells, possibly through cross-linking of a cellsurface protein. To explore this possibility and to remove any antibodydirected to any putative cell surface protein, we further adsorbed thepurified anti-DP58 reagent repeatedly on formalin-fixed freshly isolatedBM cells, and then used it to expose fresh and live BM cells for 4 hr.Interestingly, this adsorption of anti-DC reagent with fixed BM cellstotally prevented fresh BM from differentiating into BM4 cells, but itstill was capable of detecting DP58 protein in the lysates of existingBM4 cells. This indicates the presence of a cell surface molecule onfresh BM cells, which is needed for cytosolic DP58 induction. Thisobservation was corroborated using anti-DP58 peptide antibody asdescribed later.

DP58 Protein is Induced During BM Differentiation into DCs

To determine whether the BM4 cells (generated following incubation withrabbit anti-DC antisera) could differentiate into DCs, we cultivatedthem in GM-CSF for 6 days. No other cytokine such as IL4 displayed theability to generate mouse DCs, as was also shown by others [1], and BM4cells did not differentiate into DCs in the absence of GM-CSF.Phenotypic analyses revealed that BM4 cells differentiated into DCs thatclosely resembled CD8α-DCs generated from fresh BM using only GM-CSF.However while neither DCs expressed DEC-205, the DCs generated from BM4cells had a very low expression of B220 marker. Since it was difficultto categorize these cells into either lymphoid or myeloid lineages, weconsider BM4 cells as undifferentiated pDCs.

Isolation and Sequencing of DP58 from BM-Derived Cell Lysates

To determine if DP58 was a novel protein induced during BMdifferentiation into DCs, we purified it by immunoprecipitation andisolated the protein band following SDS-PAGE. This was then subjected tocontrolled tryptic digestion and the sequence of the peptides generatedwas positively identified with a computationally predicted RIKEN cDNA(NCBI data base accession NP_(—)780664).

Next we addressed whether this novel cytosolically induceddifferentiation-related protein is a glyco- or Phosphoprotein. While theperiodic acid-schiff staining for glycoprotein proved negative, thewestern blotting using a commercial anti-phospho-tyrosine antibodyreagent indicated that DP58 was a phosphoprotein induced during BMdifferentiation.

Furthermore, to identify pDCs and study DC differentiation, we developedan anti-DP58-peptide reagent using the sequence identified as Seq ID 2.We used this antibody reagent to detect the presence of DP58 inunstimulated and stimulated BM cells as well as in DCs. The resultsshowed that DP58 was undetectable in DCs possibly because of low levelsof pDCs cells expressing of DP58. It was also evident that anti-peptideantibody recognized DP58 only in differentiating BM cells such as BM4cell) lysates, and it could not stimulate fresh BM cells todifferentiate. This was expected in view of the results discussed above,leading us to conclude that DP58 is the cytosolic marker of earlyprogenitor DCs, possibly involved in signal transduction.

Discussion

This study is the first on a novel protein DP58 that was identifiedusing a polyclonal anti-DC antibody reagent. The reagent wasspecifically prepared from antisera raised against the lysates ofimmature DCs that were generated following 6-day cultivation of mouse BMcells in GM-CSF5. Before use, DCs were carefully phenotyped usingfluorescent anti-CD11c, anti-CD11b, anti-CD8α, anti-MHC-II, anti-CD80,anti-CD86, anti-CD117, anti-B220, and anti-DEC205 monoclonal antibodies.

We reasoned that this cultivation of BM cells in GM-CSF should yield notonly DCs, but also some undifferentiated BM cells that are atintermediate stages of development. The cell lysates from suchheterogeneous DC-enriched (over 95%) population would likely containvarious immunogenic molecules in a pecking order of immunogenicityderived from all cell types. This explains why our polyclonal antiserarecognize not only the antigenic components of mouse DCs but also othersassociated with the differentiating BM cells. Importantly, the specificreagent prepared from these antisera readily detects DP58 protein onlyin differentiating BM cells within 30 min, and these differentiating BMcells develop into DCs when they are exposed to GM-CSF. Moreover, thisinduction of DP58 happens long before DCs emerge from BM cells following6-day cultivation in GM-CSF. It suggests that DP58 occurs primarily inpre-DC population, and is highly immunogenic since the contribution ofpre-DC population would be minimal in the DC lysate immunogen used toraise the antisera.

Identification of DP58 with a RIKEN cDNA in the database certainlyadvances our ability to identify many hypothetical proteins. The complexprocess of bone marrow differentiation into specific cell lineages suchas dendritic cells involves numerous molecular interactions. Specificcytokines such as GM-CSF is known to drive mouse BM-associated HSC toDC-specific development and give rise to committed progenitor stemcells. Since GM-CSF or our specific antibody reagent can both cause BMcells to differentiate via induction of DP58 phosphoprotein, and sincethe antibody reagent in particular detects DP58 in cell lysates within30 min of BM cultivation as mentioned earlier, this is suggestive ofongoing intracellular events. Furthermore, the fact that anti-DP58peptide antibody generated based on the sequence of DP58 also detectsthis protein only in lysates of differentiating but not freshundifferentiated BM cells or DCs lends further support to thiscontention. This also suggests that this protein is induced as a resultof activation and that this activation is possibly coordinated through aphosphorylation event.

Furthermore, to our knowledge, there is no specific method to generateand propagate early progenitors. On the basis of phenotypic studies, theBM4 cells reported here certainly fit the description of some of theearly DC progenitors [8,9]. Since these cells can be cultivated for ashort period in the absence of GM-CSF, it provides us the ability toclone or enrich and functionally characterize these DC progenitors fromthese cells. Further investigation is in progress to elucidate thephysiological role and significance of BM4 cells in the context of DP58induction during BM differentiation.

Example 2 CSP82

In this Example, we report identification and partial characterizationof this cell-surface molecule as the mouse lactoferrin precursorglycoprotein, named CSP82. We show that both DP58 induction and thegeneration of early DC progenitors are mediated via this cell-surfaceprotein. In contrast to lactoferrin found in milk, colostrums, and othermucosal secretions; CSP82, a member of iron-transporting transferrinfamily, occurs on naïve BM stem cells, but not on mature descendants. Toour knowledge, this is the first report that lactoferrin precursorserves as a BM cell surface protein in the induction of a cytosolicdifferentiation marker DP58 associated with the emergence of aCD11b++Gr1++++B220+ progenitor DCs.

Materials and Methods

Mice. See, Example 1.

Antibodies. Antibodies were prepared substantially as described inExample 1 and as further described below.

DC Generation. DCs were generated substantially as described inExample 1. Generation of DCs from BM-derived stem cells. We firstisolated hematopoietic stem cells (HSCs) using a commercial kit (fromStem Cell Technology, Canada) according to the manufacturer's protocol.The isolated HSCs were directly incubated at 4° C. with specificanti-CSP82 antibody for 4 hr generating BM4-HSC. Lysates from the latterwere subjected to SDS-PAGE and Western blot analysis to demonstrateinduction of DP58 as reported in Example 1.

Specific antibody reagents. Rabbit anti-DC antibody and anti-DP58antibody reagents were prepared substantially as described in Example 1.These reagents were used respectively to generate progenitor DCs anddetect DP58 on western blots. The rabbit anti DC Reagent A (henceforwardreferred to as Reagent A) was obtained by repeated sequential adsorptionof anti-DC antisera at 4° C. on cells from spleen, liver, BM-derivedmature and immature DCs and myeloma X63-Ag 8.653 until it testednegative on western blots of normal tissue lysates. Rabbit anti-DCReagent B (henceforward referred to as the Reagent B) was prepared byfurther adsorption of Reagent A with formalin-fixed BM cells. Reagent Ais capable of generating progenitor DCs and inducing marker proteinDP58, whereas, Reagent B detects DP58 in pDCs but cannot induce it.These reagents were further purified on Protein A-agarose affinitycolumns.

Generation of early DC progenitors. This was done substantially asdescribed in Example 1.

Identification of CSP82 by repeated adsorption. The initialidentification, and isolation of CSP82 was done using Reagent A. Thiswas confirmed using specific anti-CSR82 antibody developed subsequently.

Rabbit antisera against CSP82 peptide. The CSP82-specific Peptide SEQ IDNO: 2 (IPIGTLRPYLNWNGPPASLE)-conjugated to keyhole limpet hemocyanin(KLH) was used as the immunogen (100 μg/intradermal injection).Initially the conjugate was emulsified in Complete Freund Adjuvant (CFA)and subsequently in Incomplete Freund Adjuvant (IFA). Rabbits wereboosted with CSPR82-peptide KLH, bled every 10 days, and the antiserawas tested and purified by salt fractionation and affinitychromatography as described in Example 1.

Detection of CSP82 and DP58. Initially, reagent A was used to detect andisolate BM cell surface protein CSP82, while reagent B was used only todetect cytosolic DP58 in progenitor DCs. Detection and monitoring CSP82and DP58 were subsequently performed using respectively specificanti-CSP82 peptide and anti-DP58 antibodies.

SDS-PAGE and Western blot. This was done substantially as described inExample 1.

Immunoprecipitation. Protein A was used to isolate immune complexesresulting from reactions of adsorbed rabbit antibody with fresh bonemarrow lysates as described in Example 1. The protein band obtained bySDS-PAGE was sequenced by peptide mass fingerprinting at proteomics CoreLaboratory of Dr. Wang Mu, Indiana University School of Medicine,Indianapolis.

Results

The 82 kiloDalton Protein CSP82 Identified on the Cell Surface of FreshMurine BM Cells

To identify CSP82, freshly harvested BM cells of naïve BALB/c mice weresubjected to SDS-PAGE and western blotting. The blot was analyzed usingthe purified rabbit antibody Reagent A. The results showed that theCSP82 protein band was detectable only in lysates of fresh BM cells, andthis was possible only when non-ionic detergents like NP-40 were used.No such band was discernible in similar lysates from mature and immatureDCs (IDCs), progenitor DCs (BM4), splenocytes, or myeloma cells.However, the CSP82 protein was undetectable in the lysates of BM andother cells if the antibody Reagent B was used for western blotting.Clearly, the adsorption of rabbit antibody Reagent A on fixed-BM cellsremoved the antibody necessary for detection of CSP82 present on freshBM cells.

To assess whether CSP82 is associated with HSCs in freshly harvested BMcells, a commercial kit from Stem Cell Biotechnology was used to isolateand purify HSCs. Proteins in lysates of HSCs were then separated bySDS-PAGE and analyzed by western blot. Results revealed the presence ofCSP82 in HSC lysates when the western blot was probed with Reagent A.However, with Reagent B the protein band corresponding to CSP82 wasundetectable, although the same reagent could detect, as expected, DP58in the same BM4 lysates. Thus the antibody Reagent A specificallyrecognized CSP82, an 82 kd protein in fresh BM cells.

We confirmed the above finding came from the immunofluorescence studieson fresh BM cells showing that CSP82 protein on these cells isrecognized by Reagent A and anti-CSP82 antibody only.

Isolation and Sequencing of CSP82 from Fresh BM Lysates

We isolated and purified the 82 kd protein band (CSP82) byimmunoprecipitation from lysates and separation by SDS-PAGE. Thisprotein was then subjected to tryptic digestion, and sequencing bypeptide mass fingerprinting. The sequence of CSP82 was identical to thatof the murine lactoferrin precursor protein [11,12].

Development of Rabbit CSP82 Peptide-Specific Antibody

To better characterize CSP82 and determine its role in DC generation, wedeveloped a rabbit anti-CSP82 peptide antibody reagent using the peptidesequence of Seq ID 2. This peptide sequence is also identical to that insecreted lactoferrin [12]. We reasoned that antibody to this peptidewould not only confirm the identity of CSP82 with the lactoferrin groupof proteins, but also establish the existence of both membrane andsecreted forms of lactoferrins. Furthermore, this antibody was used toconfirm our earlier findings with the reagent A that CSP82 is present onnaïve BM or stem cells. The results showed that anti-CSP82 peptideantibody could detect CSP82 as well as secreted lactoferrin in BMlysates of fresh but not fixed BM cells. It is interesting to note thatthe specific anti-CSP82 peptide antibody recognized also the cytosoliclactoferrins of about 52 kD in both BM4 and HSC-BM4. Furthermore,incubation of fresh BM cells with this specific reagent inducedprogenitor DC, i.e., BM4 cells and expression of the cytosolic protein,DP58. Furthermore, when fresh BM cells were incubated with anti-CSP82reagent, they underwent transformation into BM4-like cells and inductionof DP58, as was seen, by the use of Reagent A. The results clearlyindicate that CSP82 was the BM cell surface protein recognized byantibody Reagent A and anti-CSP82. Moreover, binding of either antibodycould induce development of BM cells into Pro-DC BM4 cells and induceexpression of DP58 phosphoprotein. Interestingly, antibody Reagent A,unlike the anti-CSP82 peptide antibody, recognized only CSP82, or themembrane form of lactoferrin implying that the latter as a maturesurface protein might have unique epitopes, due possibly toposttranslational modifications that facilitate its localization on cellsurface.

CSP82 is a Glycoprotein

Glycoprotein staining and an antiphosphotyrosine antibody were used todetermine whether CSP82 on BM cells is a glyco- or phosphoprotein.Proteins of detergent-solubilized BM cell lysates were separated usingSDS-PAGE and then stained using a Pro-Emerald 300 glycoprotein stain kit(Molecular Probe, USA). The staining positively identified CSP82 as aglycoprotein. However, CSP82 protein proved to be unphoshphoprotein,unlike the cytosolic DP58, and this was shown by western blot analysisusing a commercially obtained an anti-phosphotyrosine antibody.

Phenotypic Characterization of Different BM Cells

We used techniques of immunofluorescence to characterize fresh anddifferentiating BM cells, as mentioned earlier. Controls run with normalpre-bleed also proved negative. We also determined whether typical DCdevelopmental markers were present on BM4-like cells. Such cell surfacemarkers as CD11b, Gr 1, B220 were easily discernible using commercialmonoclonal antibodies as the BM cells differentiated into pro-DC BM4cells.

Discussion

To our knowledge, this is the first example that shows a novel mouselactoferrin precursor protein (CSP82) is present on undifferentiated BMcells or HSCs (hematopoietic stem cells), but not on their descendants.Similar to many membrane proteins, CSP82 appears to be a glycoprotein.It is interesting to note that the membrane form of 82 kD lactoferrindescribed here is identical in amino acid sequence to the secretedlactoferrin which can be of various molecular sizes up to 79 kD. Thedifference in the nominal molecular sizes between CSP82 and secretedlactoferrin may lie in the hydrophobic sequences that are necessary tobe a membrane-associated protein. BM-associated mouse CSP82 hasconsiderable sequence homology with a human melanoma protein,melanotransferrin p97, which is a membrane form of serum Fe-bindingprotein transferrin and human lactoferrin. [11]. We believe that CSP82,like this membrane-bound p97, has a glycosyl-phosphotidylinositol (GPI)moiety as the membrane anchor. This is a posttranslational lipidmodification that occurs in endoplasmic reticulum. Experiments are inprogress to address this issue.

Occurrence of a lactoferrin member on BM stem cells must be of immensebiological significance. Lactoferrin, an iron-binding glycoprotein inmilk and other exocrine secretions, is known to have multiple functions,notably anti-microbial properties and the ability to modulate the immunesystem by release of anti-inflammatory cytokines from monocytes and byregulation of cellular proliferation and differentiation [12-14]. Theanti-microbial property of lactoferrin from leukocytes is due to itsability to bind and inactivate LPS [24]. Our finding of a lactoferrinprecursor protein on BM or HSC suggests that it may serve as a receptorfor LPS-like ligands promoting differentiation of BM cells alongCD11b+/Gr 1+ myeloid lineages. There are reports on the presence ofestrogen and growth factor response modules in the mouse lactoferringene [12,13]. This suggests that the expression of lactoferrin proteinas a cell surface receptor on stem cells may be responsive toenvironmental estrogenic substances, which in turn may influence on BMdifferentiation and proliferation [13].

This example also shows that crosslinking of this cell surface proteinon BM cells by antibody Reagent A or by the anti-CSP82 antibody sets inmotion a differentiation event in which BM stem cells become committedto the DC progenitor pathway.

Finally, the physiological role of CSP82 in HSC remains speculative. Theinteraction of CSP82 with microbial LPS may serve two purposes: (1)protect HSCs from microbial infections, and (2) trigger a novelcytosolic phosphoprotein DP58-mediated differentiation pathway leadingto DCs. The latter as APCS can up or down regulate acquired immunityinvolving B and T cells. Lactoferrin is an iron-binding protein, so itis possible that iron is a natural ligand for CSP82. Iron availabilityhas been shown to influence expression of the cyclin-dependent kinaseinhibitor P21 during differentiation of DCs from human peripheralmonocyte precursors [15].

Example 3 DP58 Expression in Brain Cells

As a first step to understand the physiological roles of DP58 in thecontext of BM differentiation, we evaluated the tissue-specificity ofDP58 and its phosphohorylation status. Using biochemical and moleculartechniques we show that DP58 is constitutively expressed in brain butprimarily as an unphosphorylated protein. Moreover, immunocytochemicalstudies demonstrate the presence of DP58 in neurons of the basalganglia, brainstem and neocortex of adult mice brains. It appears thatDP58 is primarily localized in the cell nuclei of cultured neurons.Because its expression is tissue-specific, DP58 as a nuclear proteinmarker may prove useful to monitor HSC differentiation into neuronalcells. To our knowledge, this is the first report of a common proteinshared between mature neuronal cells and differentiating bonemarrow-derived progenitor cells.

Materials and Methods

Mice—See, Example 1.

Antibody reagents—For phenotypic characterization of immature DCs and BMprogenitors, we used following monoclonal antibodies conjugated to FITC,and directed to MHC class 11, CD11b, B220, CD86, CD11c, CD8α, CD80 andCD117 (all from eBioscience, USA). Antibodies to phosphotyrosine,phosphoserine and phosphothreonine were obtained from Zymed, USA. Thesewere used in western blotting to determine the phosphorylation status ofDP58 in Pro-DCs and brain cells. Some reagents for western blotting andimmunocytochemistry were purchased from Pierce (USA). Others wereobtained as listed: anti-rabbit-HRP (ICN, USA) goat anti-rabbit Cy3,goat anti-mouse Cy2, (Amersham, USA).

DC generation—DC cells were prepared substantially as described inExample 1.

Raising antibodies against immature DC lysates—Anti-DC polyclonalantibodies and anti-DP58 antibodies were generated substantially asdescribed in Example 1.

DP58 protein—DP58 was isolated from BM cells substantially as describedin Example 1.

SDS-PAGE and Western blot—All lysates were prepared and subjected toSDS-PAGE substantially as described in Example 1. Proteins were thentransferred onto nitrocellulose for western blotting. The latter wasdeveloped with rabbit anti-DP58 peptide as the primary antibody,followed by goat anti-rabbit-Ig-HRP, and Super Signal West Picochemilumininescent substrate to visualize labeled proteins on film.

The range of DP58 occurrence in different tissues—The presence of DP58in various tissues was examined by screening multiple tissue-specificcDNAs (MTC Panels cat no. #K1441-1 and #K1430-1 from BD Biosciencesclontech, USA) by PCR. The MTC panels included cDNAs from mouse heart,spleen, and lung, liver, skeletal muscle, kidney, testis, embryos ofvarious ages, bone marrow, eye, lymph node, smooth muscle, prostate,thymus, uterus, and stomach. We also screened for DP58 by PCR, freshlyisolated bone marrow cells, brain tissues, progenitor DCs (BM4 cells),immature and mature DCs from mice of various ages and confirmed bysequencing of the amplified DNA band.

Reverse-transcriptase mediated polymerase-chain reaction(RT-PCR)—Analysis of the expression of DP58 was carried out using RT-PCRessentially as described [16]. The forward primer used was SEQ ID NO: 6(5′-ATTCTTCTGAGACGGACCTGACAC-3′) and the reverse primer consisted of SEQID NO: 5 (5′-CGCGTTGGTTTTGTAGGCTATTTC-3′). Total RNA samples wereextracted using the RNAqueous system (Ambion, USA). Reversetranscription reactions were carried out using 1 μg of total RNApurified from indicated sources. Each reaction consisted of 60 μl ofwhich 25 μl was the RNA and water. The RNA was denatured for 3 min. at70° C. then chilled on ice and the remaining reagents were added suchthat the reaction contained 1× reverse transcriptase buffer, 1 mM MgCl2,0.5 mM all 4 dNTPs, 0.5-1 μl RNase inhibitor (Promega, USA.), and 100pmole of random hexamers. The primers were allowed to anneal to the RNAat room temp for 5-10 min. Lastly, 200U SuperscriptRT (Invitrogen, Inc.)was added and the reactions incubated for 60 min at 37° C. The RNAtemplate was degraded by incubation with 1 μg of RNaseA at 37° C. for 15min.

For end-point PCR reactions, an amount of the RT reaction equivalent to16.7 ng of input RNA was subjected to the PCR. The reaction volume was25 μl containing, 1× PCR buffer, 250 μM all 4 dNTPs, 2 mM MgCl2, 10pmole of each specific PCR primer, and 2-3 units Taq polymerase.Reactions were standard 30 cycle PCRs with conditions involving aninitial 5 min. 95C denaturation followed by 30-40 cycles of 95° C. for30 sec, 62° C. for 30 sec, 72° C. for 30 sec. Following PCR, 10-15 μl ofeach reaction was analyzed by agarose gel electrophoresis andphotographed by UV transillumination. As a control for RNA loading intothe RT reaction, expression of Mus musculus glyceraldehyde 3-phosphatedehydrogenase (G3PDH) was analyzed using a 25-cycle PCR. When expressionwas to be quantified by quantitative PCR (see below), the 60 μl RTreaction was first diluted to 6-fold and 1 μl of the diluted RT was usedas template for each qPCR.

Quantitative PCR (qPCR)—Quantitative PCR was performed utilizing theMx3000P PCR machine (Stratagene, USA.). Fluorescence detection chemistryinvolved utilization of SYBR green dye master mix (Bio Rad, USA.) andHPLC purified qPCR primers at 150 nM. Each qPCR utilized 2.5 ngequivalents of input RNA from each RT reaction. All qPCR reactions werecarried out in triplicate and used a 40-cycle program whose time andtemperature parameters were the same as for end-point PCR. Melting-curveanalysis of all products demonstrated a single peak, indicating thateach set of primers produced a single product. Each RT reaction wasequalized for RNA input by assessing the level of expression of therelatively invariant housekeeping gene, G3PDH. To determine quantitativevalues, standard curves were generated with each primer pair using a 5×dilution series ranging from 16.7 ng to 0.27 ng RNA equivalents of anRT. Expression of DP58 was then equated to the normalized input ofG3PDH.

Immunohistology and immunohistochemistry-Adult mice were euthanized withan overdose of sodium pentobarbital and transcardially perfused withneutral-buffered 4% paraformaldehyde. The brains were removed andpost-fixed in the same fixative for 1 hour at room temperature on theshaker. They were then cryoprotected by immersion overnight inTris-buffer (pH 7.4) with 30% sucrose. The brains were sectioned on acryostat at a thickness of 40 μm. The sections were processedfree-floating for immunohistochemistry as follows. All rinse steps wereperformed using Tris-buffer (pH 7.4). Sections were first incubated inmethanolic peroxide for 15 minutes to remove endogenous peroxidase and,following a rinse step, blocked with 5% non-fat dry milk for one hour atroom temperature. They were then directly transferred to the primaryantibody, DP58, diluted 1:500 in 5% non-fat dry milk for 2 hours at roomtemperature and then overnight at 4° C. The next day, following a rinsestep, the sections were incubated in peroxidase-conjugated goatanti-rabbit secondary antibody (diluted 1:100) for 3 hours at roomtemperature on the shaker. Following another rinse step, theimmunolabeling was visualized by incubation with diaminobenzidine andhydrogen peroxide. The sections were mounted on alcohol-gelatinizedslides and cover-slipped with Permount.

A similar procedure was used for immunohistofluorescence with thefollowing differences: no endogenous peroxidase step was performed; theblocker was 3% normal goat serum; the primary antibody was mixed in 1%normal goat serum; and the secondary antibody was Cy3-linked goatanti-rabbit IgG, diluted 1:1000.

Sections were also double-labeled using DP58 antibody and a mouseantibody to microtubule-associated protein 2 (MAP2; Sigma product #M-1406; diluted 1:250) as a neuronal marker. The secondary antibodieswere Cy3-linked goat anti-rabbit IgG and Cy2-linked goat anti-mouse IgG,both diluted to 1:1000.

Primary neuron culture: The primary neuron culture method was adaptedfrom Brewer [17]. Briefly, the hippocampus was isolated by dissectionfrom mice brain, minced on a tissue chopper, incubated in Hibernate A(Gibco), and then treated with Papain (Worthington). The tissue was thentriturated 10 times and the supernatant collected. The sediment wasresuspended in Hibernate A/B27 (Gibco) and triturated again. Thisprocedure was repeated once more with the supernatant saved each time.The collected supernatant was then layered on an Opti-Prep gradient andcentrifuged for 15 minutes at 1900 rpm. The volume above the whitesuspension layer containing the neurons was discarded and the whitesuspension layer was transferred into Hibernate A. This was centrifugedat 1100 rpm at room temperature. The supernatant was discarded and thepellet resuspended in B27/Neurobasal A (Gibco). The neurons were platedat a density of 1×107 in Poly-D-Lysine-coated glass 96-well cultureplates containing B27/Neurobasal A. The cells were incubated for 1 hourat 37° C. in 5% CO2, rinsed with fresh B27/Neurobasal A at 37° C. thenHibernate A and incubated in growth medium. The cells were fed everyother day and allowed to grow for 1 week before experiments wereconducted.

Results

DP58 Expression in Different Tissues

Expression of DP58 protein in various tissues was assessed by screeningPCR multiple tissue-specific cDNAs (MTC Panels) using DP58-specificprimers. The results indicated that only the cDNA from brain tissuescould be amplified using DP58-specific primers. Further corroboration ofthis finding came from RT-PCR and qPCR analyses of DP58 expression infreshly isolated whole brain, bone marrow cells, and cells generatedduring DC differentiation. DP58 expression at the mRNA level inunstimulated brain far exceeded the levels seen in BM cells even after40 cycles of PCR. The expression of DP58 message in brain and bonemarrow was quantified by qPCR. Brain tissue expressed approximately 1200times more DP58 mRNA than BM cells, particularly in dendritic progenitorcells BM4, when all DP58 levels were normalized with respect to thehousekeeping gene G3PDH. Interestingly, DP58 mRNA level was four timeshigher in cycloheximide treated BM4 cells than in untreated BM4 cellsindicating that the factor(s) required for DP58 transcription arealready present prior to the induction of BM cells [18]. Treatment withcycloheximide was indeed inhibitory upon protein synthesis as reflectedby the fact that the level of DP58 protein was not increased fourfold inconcert with that of the mRNA. Our result also indicated that unlikeDCs, brain tissues constitutively expressed DP58 protein.

DP58 Protein Expression in Brain and Bone Marrow Cells

The demonstration that levels of DP58 mRNA level were higher in brainthan in bone marrow cells raised the question of whether similarrelative concentrations would be observed at the protein level in bothtissues. By SDS-PAGE and Western blotting, we showed that contrary towhat was seen with RT-PCR, DP58 protein is much higher in BM4 cells thanin brain. Also, the estimated molecular weights were different. In braintissue, DP58 migrated with an apparent MW of 52 KDa. Even though onlyBM4 cells express DP58 protein, both BM4 and immature DCs expressedsimilar levels of DP58 mRNA. Furthermore, in spite of several-fold highDP58 mRNA expression in unstimulated whole mouse brain tissue, it didnot translate into proportionally high DP58 protein levels.

Comparison of DP58 Nucleotide Sequences from Brain and BM 4 Cells

The PCR products derived from brain and bone marrow, using theDP58-specific primers were sequenced and shown to be identical. Inaddition, the sequences were identical to the corresponding region ofthe RIKEN cDNA identified as DP58.

Demonstration of DP58 Expression in Brain by Immunohistology

Using the DP58 peptide-specific antibody (Reagent A)-we performedimmunohistology on brain tissue sections. The results showed DP58immunoreactivity in all mouse brain regions. The nuclei of nerve cellswere immunolabeled in all cortical layers, in the pyramidal layer andthe dentate granular layer of the hippocampal formation, in the basalganglia and brainstem. A closer look revealed that the nuclear labelingconsisted of a diffuse labeling of the entire nucleus and an intenselabeling of bodies, approximately 5 μm in diameter. In the neocortex,the intense labeling appeared primarily at the periphery of the 5μmbodies. In the brainstem, the labeled bodies were more punctate inappearance and could also be seen in the perikaryon. The same pattern ofimmunoreactivity was also seen in the cerebellum, where the nuclei ofPurkinje cells were clearly labeled, although the nuclei of granulecells were not. These results confirm that DP58 is a cytosolic proteinin BM4 and suggest that DP58 may be synthesized in the neuronalperikaryon and subsequently transported into the nucleus.

DP58 protein was localized in stimulated BM cells (BM4) and in nervecells using confocal microscopy in conjunction with specific antibodyregents (rabbit anti-DCs) and goat anti-rabbit Cy3. As a control, normalgoat serum was used instead of the primary antibody. The results showedDP58 localized to the nuclei of nerve cells but in BM4 cells, DP58labeling was cytoplasmic. Cells labeled by the DP58 antibody were alsolabeled by the MAP2 antibody, an antibody that is specific for neurons.As shown in previous study by Western blotting [19], DP58 was detectableonly as a cytosolic protein in BM4 Pro-DC cells. The method control wasrun with normal goat serum.

Post-Translational Modification of DP58 in Different Tissues

Since SDS-PAGE and western blotting of DP58 from BM4 cells and brainrevealed two distinct molecular species, 58 KDa and 52 KDa respectively,it was of interest to determine if post-translational modification wouldaccount for the difference. We performed SDS-PAGE and western blottingof brain tissue, naive BM and BM4 cells using commercially obtainedanti-phosphotyrosine, antibodies. The results indicated specificphosphoprotein nature of DP58 in BM4 cells only but not in brain. Thus,DP58 occurred as an unphosphorylated 52 kDa nuclear protein in brainwhile in pro-DC cells, DP58 is phosphorylated [19].

Discussion

The evidence presented in this example clearly shows that DP58expression does not occur exclusively in BM-derived early progenitorDCs. Expression of this novel molecule is also observed in braintissues. Using qPCR we have demonstrated that there is 1200 times moreof DP58-specific mRNA in mouse brain than in BM-derived BM4 cells.However, BM4 cells express higher levels of DP58 protein than do braintissues. Parallel sequencing of the products of PCR-amplified DP58 frombrain tissue and BM4 cells reveals complete identity with the DP58protein sequence.

The two interesting points emerge from analyses of the results of thisstudy. First, of all tissues, only cells of the immune system and brainexpress DP58, and these tissues are derived from different germ layers.Immunocytochemical studies clearly indicate that DP58 is predominantlylocated in neuronal nuclei, whereas in BM4 cells, it is cytosolic. Thetwo proteins also differ in observed molecular weight; the 58 kDa aprotein in BM4 cells is a phosphoprotein, while in neuronal cells it isa 52 kDa unphosphorylated protein. The apparent difference in size maybe due to phosphate moieties in DP58. The other noteworthy point is thatalthough at the mRNA level, the brain tissues exhibit considerablyhigher levels of DP58 than in BM4 cells, this does not happenproportionately at the protein level. Western blot analysis using thesame protein amounts from brain and BM4 cells shows that the expressionis highest in the latter. In BM-derived progenitors, the protein isinduced during BM4 differentiation, whereas in nerve cells from diverseregions such as cortex, brain stem, and basal ganglia, DP58 expressionoccurs constitutively. A low detectable level of immunostainablecytosolic DP58 is, however, also discernible in nerve cells byimmunocytochemistry. It remains to be determined whether the cytoplasmicneuronal protein is phosphorylated as in BM4 cells.

An issue of interest is why brain cells express significantly higherlevels of DP58 mRNA, and yet at the protein level, expression is evenless than that in BM4 cells. Also intriguing is the fact that the levelof DP58 mRNA is higher in naïve BM cells than in BM4 cells, yet theprotein is higher in the converse order. To address this disconnectbetween the levels of DP58 mRNA and protein, we treated cells withcycloheximide to inhibit protein synthesis. It is apparent from ourstudy that cycloheximide causes DP58 mRNA levels to rise four fold inBM4 cells, but when the same cells were analyzed at the protein level,they did not register proportionately higher values. Thus, it appearsirrespective of whether it is in brain or BM4 cells that the translationof specific mRNA into DP58 protein is highly regulated. Since thetranscription process does not seem to be hindered, this regulationpossibly occurs at the post-nuclear processing stages. However, it maybe likely that the BM4 induction process leads to the activation of aregulatory pathway resulting in DP58 mRNA degradation. The synthesis ofthe enzyme responsible for this mRNA turnover is likely to be inhibitedin the presence of cycloheximide thus accounting for the 4-fold increasein DP58 mRNA in inhibitor treated cells.

The differences in DP58 occurrence between brain and BM4 cells may beexplained in terms of their differentiation status. BM4 cells representdifferentiating DC progenitors, whereas neurons are adult quiescentcells unlikely to respond to any differentiation stimuli. Nuclearlocation of DP58 in neurons may reflect an anti-apoptotic property tomaintain G₀ status in a manner similar to that observed with BCL3proteins [20]. Neurogenesis and neuronal maturation may accompanyredeployment in the nuclei of DP58 as an unphosphorylated constitutiveprotein from an inducible cytosolic phosphoprotein.

During neurogenesis, i.e., in a child over 2 years of age, when neuronsreach some stages of maturity, DP58, as an important anti-apoptoticfactor is expected to be expressed and deployed in neuronal nuclei as anIndication of a normal developmental process. Any changes in the levelof DP58 may be a phenotypic measure of neuronal viability or generaldevelopmental problem. In pre-natal stage too, it may have implicationsin health of developing fetuses. In cases of neuroblastoma, DP58expression may significantly vary due to persistence of immatureneurons. Any treatment modality that improves the condition may benefitby monitoring DP58 level in effuent cells or biopsies. ELISA, RIA or PCRwill reveal these changes. In diseases like Alzheimer's Disease orothers, the measurable levels of DP58 would be indicative ofinfiltration of cells like dendritic cells and the consequentimmunological reaction or neuronal degeneration and dysfunction.

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1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. A method of inducing expression of DP58which comprises incubating BM cells with anti-DC antibodies.
 9. Themethod of claim 8 in which early progenitor undifferentiated DCs aregenerated.
 10. An isolated BM cell surface protein which, in BM cells,is activated by anti-DC sera to induce expression of DP58 and thatcomprises the sequence of SEQ ID NO:
 2. 11. The CSP of claim 10 that hasa molecular weight of 82 KD.
 12. The CSP of claim 10 that has thesequence:   1 MRLLIPSLIF LEALGLCLAK ATTVRWCAVS NSEEEKCLRW     QNEMRKVGGP  51 PLSCVKKSST RQCIQAIVTN RADAMTLDGG TMFDAGKPPY     KLRPVAAEVY 101 GTKEQPRTHY YAVAVVKNSS NFHLNQLQGL RSCHTGIGRS     AGWKIPIGTL 151 RPYLNWNGPP ASLEEAVSKF FSKSCVPGAQ KDRFPNLCSS     CAGTGANKCA 201 SSPEEPYSGY AGALRCLRDN AGDVAFTRGS TVFEELPNKA     ERDQYKLLCP 251 DNTWKPVTEY KECHLAQVPS HAVVSRSTND KEEAIWELLR     QSQEKFGKKQ 301 ASGFQLFASP SGQKDLLFKE SAIGFVRVPQ KVDVGLYLTF     SYTTSIQNLN 351 KKQQDVIASK ARVTWCAVGS EEKRKCDQWN RDSRGRVTCI     SFPTTEDCIV 401 AIMKGDADAM SLDGGYIYTA GKCGLVPVLA ENQKSSKSNG     LDCVNRPVEG 451 YLAVAAVRRE DAGFTWSSLR GKKSCHTAVD RTAGWNIPMG     LLANQTRSCK 501 FNEFFSQSCA PGADPKSNLC ALCIGDEKGE NKCAPNSKER     YQGYTGALRC 551 LAEKAGNVAF LKDSTVLQNT DGKNTEEWAR NLKLKDFELL     CLDDTRKPVT 601 EAKNCHLAIA PNHAVVSRTD KVEVLQQVVL DQQVQFGRNG     QRCPGEFCLF 651 QSKTKNLLFN DNTECLAKIP GKTTSEKYLG KEYVIATERL     KQCSSSPLLE 701 ACAFLTQ


13. (canceled)
 14. (canceled)
 15. (canceled)
 16. The method of claim 9which comprises: (a) isolating BM stem cells with panning on anti-CSP82kd coated plates, (b) generating DP58+ cells (BM4) by stimulation withanti-CSP82, and (c) inducing DCs by further incubation in GM-CSF in ashorter period than necessary without this step.
 17. (canceled) 18.(canceled)
 19. A method of suppressing expression of a marker of BM stemcell differentiation that comprises suppressing expression of DP58 withantisense DP58 DNA or RNA.